This invention relates generally to means of forming laser beams, and, more particulary, relates to a means for combining divergent congugate laser beams.
The laser beam of this invention is directed at a conventional magneto-optic stripe domain light deflector which is a phase diffraction grating such that both the grating constant and the orientation can be altered by application of an external magnetic field. The diffraction grating consists of a ferri- or ferro-magnetic film containing stripe domains which by virtue of the Faraday effect act as a diffraction grating. Both the orientation and spatial periodicity of the stripe domains can be controlled by application of a magnetic field from external coils. The deflector is two dimensional, fast and very wide angle. It has many applications including displays, optical radar, communications, multi-target designation and tracking, reconnaissance, non-impact printing, etc. When a laser beam impinges on the stripe domain phase grating backed by a mirror, two beams of equal intensity emerge in the two first order diffraction angles. As a result, the two beams go in different directions and unless a beam combiner is used, the energy in the conjugate beam is wasted.
In the apparatus shown in the G. F. Sauter, et al, U.S. Pat. No. 4,148,556 there is illustrated a magneto-optic light deflection system that utilizes the magnetic film diffraction grating of the E. J. Torok, et al, U.S. Pat. No. 3,752,563, but in which the light is transmitted by optical fiber transmission lines. In this magneto-optic light deflection system, a light beam is directed normally incident to the first surface of the magnetic film by an input optic fiber and is coupled to selected ones of output optic fibers on the second and opposite surface of the magnetic film by applying the desired magnetic fields to the magnetic film. Conjugate reflected light beams are, via their associated output optic fibers, added together by an optic coupler to provide a single output fiber having the sum of the light intensity in both of the associated output fibers.
The use of optic fibers causes line losses and restrictions due to the use of optic fiber transmission lines.
In the apparatus shown in Harvey et al, U.S. Pat. No. 4,281,905 the magneto-optic light deflector system includes two converging half-lenses of equal focal lengths, that may be formed from a single circular converging lens, a circular center portion may be removed and which then may be cut in half along a diameter. The two converging half-lenses are oriented: superposed with their optical axes common and orthogonal to the plane of the magneto-optic light deflector; with their optical axes aligned with that of the optical axis of the light beam that is directed normally incident to the plane of the magneto-optic light deflector; with the two converging half-lenses separated from each other by a distance equal to twice the focal length of a single converging half-lens; and the converging half-lens located nearest the plane of the magneto-optic light deflector may be separated from the magneto-optic light deflector by a distance equal to the focal length of a single converging half-lens. An additional converging lens may be oriented in the optical axis of the parallelized conjugate light beams with its optical axis parallel thereto for focusing the two parallelized conjugate light beams upon a screen or detector that is located at the converging lens's focal plane.
The problems associated with the lens recombination device are the lens aberation and the correct positioning of the lens, five degrees of freedom per lens.
These drawbacks have motivated the search for alternative devices that minimizes the problems noted above.